1. People don’t trust him because he tells lies.

 -> If he didn't tell lies, people would trust him.

2. She is so busy that she can’t come to the party.

-> If she weren't so busy, she could come to the party.

3. I think you should play sports to keep fit.

-> If you play sport, you can keep fit.

4. I haven’t got the money, so I’m not going on holiday.

-> If I had the money, I would be going on holiday.

5. He often gets bad marks because he is lazy.

-> If he weren't lazy, he wouldn't often get bad marks.

6. Do it now, or you will not finish it on time.

-> If you don't do it now, you won't finish on time.
 

7. Hurry up, or we will be late for the exam​​

-> If we don't hurry up, we will be late for the exam​

8. Be quiet, or you will not understand the lesson.

-> If you weren't quiet, you will not understand the lesson.

9. I’m not a doctor , so I can’t help you.

-> If i were a doctor, i could help you

10. They do not understand you because you do not often talk to them.

-> If you talked to them more often, they would understand you.

11. I’m so busy , so I don’t write to my friends regularly.

-> If I weren't busy, I would write to my friends regularly.​

12. The office may be closed, so Mark won’t be able to get in.

-> If  the office is closed,  Mark won’t be able to get in.

13. You should take exercise regularly because that’s the way to get fit.

-> If  you take exercise regularly, you will get fit.

14. You can’t look the word up because you haven’t got a dictionary.

-> If  I had got a dictionary, I could look the word up ​